In 2004, Parisian police were assigned to do a training exercise in a previously uncharted part of the Catacombs of Paris beneath the Palais de Chaillot. Entering the catacombs through a drain, officers first came across a sign that read "Building site, no access," and a bit further in, a camera that actively recorded images of those who passed. As the officers approached the camera, a recording of dogs barking was triggered.
What they discovered next took them completely by surprise . . .
